AS Chemistry question

X contains 1 metal ion and one anion.
A flame test was carried out on X.
A lilac flame --> K+ ion.

A sample of X was heated and the gas evolved tested.
A gas is given off which relights a glowing spill
The gas is oxygen
X has the formula.....? :confused:

i thought it would be KNO3.
KNO3 --> KNO2 + O2
However the mark scheme says KNO2. Why?

Reply 1

raj1234

becasue k has oxidation state of +1, nitrogen +3 and oxygen -2, which add up to which is the oxisation sate of the whole molecule

anyone else?

Hmm ... I agree with you (Apart from your equation not being balanced :wink:

), I don't think nitrites decompose upon heating so I don't think the original compound could be KNO2. KNO3 makes so much more sense.

Reply 4

Christophicus

oxymoron

Hmm ... I agree with you (Apart from your equation not being balanced :wink:

), I don't think nitrites decompose upon heating so I don't think the original compound could be KNO2. KNO3 makes so much more sense.

thankyou. I'll talk to my teacher today about it. He hates edexcel because of their dodgy mark schemes.

Reply 5

Magician

oxymoron

Hmm ... I agree with you (Apart from your equation not being balanced :wink:

), I don't think nitrites decompose upon heating so I don't think the original compound could be KNO2. KNO3 makes so much more sense.

yep, i second that. I think that KNO2 is due to KNO3 that hasn't been fully reduced and is left as the nitrite (cos we dont live in an ideal world :frown:

)

Reply 6

Christophicus

Mathemagician

yep, i second that. I think that KNO2 is due to KNO3 that hasn't been fully reduced and is left as the nitrite (cos we dont live in an ideal world :frown:

)